Java Reference
In-Depth Information
a better user experience by vetting data input and providing a UI specific to the applica-
tion. For example, a dedicated Java ME messaging application can provide a threaded
interface to message conversations instead of the e-mail inbox messaging metaphor used
by most native wireless-terminal messaging applications.
Introducing Short Message Service
SMS is the oldest of the wireless messaging protocols in widespread use today. Originally
defined by the Global System for Mobile (GSM) standard in 1985, the protocol is now
used by some estimated 2.4 billion active users exchanging trillions of messages annually.
All major terrestrial cellular networks support some form of (generally interoperable)
SMS now, and many satellite communications networks do as well.
SMS messages consist of short (typically 160 characters compressed into 140 bytes)
packets sent between users on the same or disparate networks. SMS messages are routed
by an SMS Center (SMSC) and are said to be
mobile-originated
(MO) or
mobile-
terminated
(MT). When sent between users, messages are typically text, although the
protocol supports binary payloads as well. The binary formats SMS supports can be used
to send and receive ring tones and pictures, or concatenate multiple messages so that
longer text or binary messages can be sent. On most networks, you can address an SMS
message to a specific port, so that different applications can communicate on dedicated
ports, much like on the TCP/IP network. The SMS network is highly reliable, but message
delivery is not guaranteed; for example, a recipient might have her wireless terminal
switched off, and an SMS message may not be delivered to her terminal before the net-
work decides the message is too old to be delivered and discards it entirely.
On most of today's cellular networks, SMS
aggregators
provide you with the option to
send and receive SMS messages from servers on the Web. Using an aggregator, you can
arrange to obtain the rights to use a
short code
—a number of a few digits, such as 40404—
as an end point from which to originate and receive messages. Users can address a
specific server via the aggregator by using the short code, just as they would send a mes-
sage to a specific phone number.
Introducing Multimedia Messaging Service
After seeing the success of SMS, network infrastructure providers and carriers worked
together to develop MMS—a separate protocol used to transport rich multimedia mes-
sages between handsets. Unlike SMS, which is limited to simple formatted text messages,
polyphonic ring tones, and small bitmaps, MMS messages can carry digitized audio, rich
text, and images captured by cameras on today's wireless terminals. Riding atop any one
of a number of wireless protocols including SMS or TCP/IP, MMS use is growing as users
continue to originate and share content between wireless terminals.
